Thanks to spontaneous polarization in molecular structure, piezoelectric polymer, poly(vinylidene fluoride) (PVDF) holds great potential for diverse applications such as organic memory and electromechanical devices. However, the transformation of PVDF into a highly polarized β‐phase has still relied on conventional processes such as repeated mechanical strain, high‐temperature heat treatment, and high‐voltage electric poling, which are time‐consuming and can potentially cause undesired damages. Here, an ultrafast and reversible digital patterning process to transform the polymorphic phase of the PVDF has been developed using the interaction of laser with molecular structure. Plasmonic gold nanoparticles realize the interaction between PVDF and laser by increasing the absorption of the laser and amplifying its characteristics. The parameters of the laser process for phase conversion are designed under the theoretical background based on molecular dynamics (MD) simulation, and through this, the process is able to freely convert phases by simple parameter modifications. The selective laser process enables a monolithically integrated heterogeneous phase of PVDF which is not allowed in conventional single‐phase producing processes. Moreover, a practical soft robot that can control its direction has been developed by utilizing the difference in mechanical responses of each phase to the electric field in a monolithically integrated single functional layer.

Digital Selective Reversible Phase Control of Monolithically Integrated Heterogeneous Piezoelectric Polymer for Frequency Dependent Unimorph

Experiments were carried out on Form I uniaxially and biaxially stretched Polyvinylidene Fluoride (PVDF) samples to characterize their electromechanical response. The piezoelectric constants were measured at different values of superimposed strains or loads and at different values of frequencies of dynamic strains, which were applied in the longitudinal and transverse direction. It was also found through experiments that, the piezoelectric constants of PVDF are affected by the frequency of loading and there seems to be some dependence of the phase difference between the electrical and mechanical response on the superimposed strains. The tests also confirm to some extent, the results obtained by other researchers, that the piezoelectric constants increase in the longitudinal direction with increasing superimposed strains and decrease in the transverse direction for uniaxially stretched PVDF.

S. Sathiya-Naarayan

Papers

Electromechanical Behavior of Form I Uniaxially and Biaxially Stretched PVDF